The present application is based on and claims priority under 35 U.S.C xc2xa7 119 with respect to Japanese Patent Application No. 2000-261793 filed on Aug. 30, 2000, the entire content of which is incorporated herein by reference.
The present invention is generally directed to a vehicle seat. More particularly, the present invention pertains to a vehicle seat reclining apparatus for adjusting the reclining angle of a seat back relative to a seat cushion so as to be fixed at a desired angular position.
An example of a known seat reclining apparatus is disclosed in U.S. Pat. No. 5,779,313. This known seat reclining apparatus includes a lower arm secured to a seat-cushion, an upper arm fixed to a seat-back and pivotally connected to the lower arm, an inner gear portion formed in the upper arm, and a pawl slidably mounted on the lower arm. The pawl has an outer gear portion which is capable of being engaged with the inner gear portion and is movable between a meshed position at which the inner gear portion is in meshing engagement with the outer gear portion and a mesh-released position at which the inner gear portion is out of meshing engagement with the outer gear portion. A mesh regulation portion is formed at the upper arm to hold the pawl in its mesh-released position when engaged with the pawl, and an urging member is rotatably supported by the lower arm and holds the pawl in its meshed position when engaged with the pawl.
In this known seat reclining apparatus, a cam is provided with a first projection which engages the mesh regulation portion, a second projection by which the urging member and the pawl are associated with each other, and a cam surface which engages the urging member. The outer gear portion and the cam surface are formed on outer and inner surfaces of the pawl, respectively. The first projection and the second projection are formed by half die stamping on the pawl such that the first and second projections project in the thickness direction of the pawl.
With the aforementioned structure, the engagement between the cam surface of the pawl and the urging member causes the pawl to be held in the meshed position, whereby the outer gear portion of the pawl is held to mesh with the inner gear portion of the upper arm to restrict the upper arm rotation relative to the lower arm. On the other hand, rotating the urging member results in the pawl being shifted from its meshed position to the mesh-released position by urging the second projection while the engagement between the cam surface of the pawl and the urging member is released. In addition, the first projection of the pawl is brought into engagement with the mesh regulation portion to hold the pawl in its mesh-released position so that the outer gear portion of the pawl is kept released from the inner gear portion of the upper arm. Thus, the upper arm is allowed to rotate relative to the lower arm.
In the aforementioned known seat reclining apparatus, the cam surface is formed on the inner surface of the pawl and the outer gear portion is formed on the outer surface of the pawl. Further the first and second projections are formed on the pawl in the thickness direction of the pawl. Therefore, the width of the pawl from the cam surface to the outer gear portion is necessarily large to comprise the projections. This configuration results in the known seat reclining apparatus being relatively large in terms of its diameter.
Reducing the size of the apparatus in the radial direction could be established by making the radial dimension of the urging member smaller. However, in such a case, to release the engagement between the cam surface of the pawl and the urging member, the rotation angle range of the urging member should be larger, and this arrangement has the potential for resulting in a bad operational feeling.
Thus, a need exists for a seat reclining apparatus having a smaller size, particularly in terms of its diameter.
According to one aspect of the invention, a seat reclining apparatus includes a lower arm adapted to be secured to a seat-cushion, an upper arm adapted to be fixed to a seat-back and pivotally connected to the lower arm, an inner gear portion formed in the upper arm, and a pawl slidably mounted on the lower arm and having an outer gear portion which is engageable with the inner gear portion. The pawl is movable between a meshed position at which the inner gear portion is in meshing engagement with the outer gear portion and a mesh-released position at which the inner gear portion is out of meshing engagement with the outer gear portion. A mesh regulation portion is formed at the upper arm and holds the pawl in its mesh-released position when engaged with the pawl, an urging member is rotatably supported by the lower arm and holds the pawl in its meshed position when engaged with the pawl, a first engaging portion is formed at the pawl and is adapted to engage the mesh regulation portion, and a second engaging portion is formed at the pawl and is adapted to engage the urging member. An associating portion is also formed at the pawl and transmits rotation of the urging member to the pawl to slide when engaged with the urging member. The outer gear portion, the first engaging portion, the second engaging portion, and the associating portion are arranged in such an order along the radially inward direction of the pawl.
Preferably, the pawl is formed with a stepped portion so that the pawl has a radially inward portion and a radially outward portion which are of different phases or are axially offset with respect to thickness direction of the pawl. The stepped portion has an inside surface opposing the urging member and on which the second engaging portion is formed, while the stepped portion has an outside surface opposing the mesh regulation portion and on which the first engaging portion is formed.
The associating portion is preferably formed at the radially inward portion and is located more radially inward than the stepped portion of the pawl, while the first engaging portion is formed at the radially outward portion and is located more radially outward than the stepped portion of the pawl.
According to another aspect of the invention, a seat reclining apparatus includes a lower arm adapted to be secured to a seat-cushion, an upper arm adapted to be fixed to a seat-back and pivotally connected to the lower arm, an inner gear portion formed at the upper arm, and a pawl slidably mounted on the lower arm. The pawl has a stepped portion so that the pawl includes a radially inward portion that is axially offset from a radially outward portion, with the radially inward portion having a radially inwardly facing end surface and the radially outward portion having an outer gear portion. The pawl is movable between a meshed position at which the inner gear portion is in meshing engagement with the outer gear portion and a mesh-released position at which the inner gear portion is out of meshing engagement with the outer gear portion. A mesh regulation portion is formed at the upper arm to hold the pawl in the mesh-released position when the mesh regulation portion is engaged with the pawl and an urging member is rotatably supported by the lower arm to hold the pawl in the meshed position when the urging member is engaged with the pawl. A first engaging portion is formed at the pawl and adapted to engage the mesh regulation portion, and a second engaging portion is formed at the pawl and is adapted to engage the urging member. One of the urging member and the pawl is provided with a pin that engages a slot in the other of the urging member and the pawl so that rotation of the urging member causes sliding movement of the pawl. The second engaging portion is positioned radially outward of the end surface of the radially inward portion of the pawl.